Although inflammation is increasingly believed to be involved in the development of prostate cancer, responsible cause(s) of inflammation are still unknown. One promising, possible responsible cause is Trichomonas vaginalis infection (trichomonosis). Trichomonosis is a common, sexually transmitted protozoan infection known to involve the prostate. We previously investigated a history of trichomonosis and risk of prostate cancer in three epidemiologic studies, two of which observed a positive association between T. vaginalis serostatus and prostate cancer risk, particularly aggressive or late-stage disease. Although these findings are promising, additional studies are necessary to determine whether they are due to non-causal mechanisms, such as chance or residual confounding. One way to begin to investigate the validity of these findings is to examine evidence of prostatic trichomonosis in men with prostate cancer under the assumption that, if trichomonosis is truly associated with risk of prostate cancer (at least by the most commonly cited mechanisms of infection-related carcinogenesis), evidence of either past or current prostatic trichomonosis should be observed among men with prostate cancer. Therefore, as the first important step to investigating the validity of previous findings, we propose to conduct a comprehensive investigation of prostatic trichomonosis in a sample of prostate cancer patients enriched for T. vaginalis seropositive men at Washington University School of Medicine. Specifically, in this sample of men, we propose to: 1) investigate evidence of current prostatic trichomonosis or residual trichomonad DNA/antigens from incompletely cleared past prostatic infections;2) investigate evidence of past, cleared prostatic trichomonosis;and 3) determine the level of agreement between serologic and prostatic evidence of trichomonosis to inform the possible level of exposure misclassification in epidemiologic studies of T. vaginalis serology and prostate cancer risk. To our knowledge, our study will be the first to comprehensively investigate prostatic trichomonosis among men with prostate cancer. In addition to its novelty, this study is also timely and important because it expands upon and supports recent, promising epidemiologic findings, which, if ultimately confirmed, could lead to novel primary preventive strategies for prostate cancer, such as trichomonosis prevention, screening and treatment of existing infections, and possibly vaccination. PUBLIC HEALTH RELEVANCE: The proposed study is relevant to public health because it investigates the validity of recent promising, epidemiologic findings between a history of Trichomonas vaginalis infection (trichomonosis), a common sexually transmitted infection, and subsequent risk of prostate cancer. If these findings are ultimately confirmed, they could lead to the development of novel, simple and inexpensive primary preventive strategies for prostate cancer, such as trichomonosis prevention through reduced high-risk sexual behaviors;screening and treatment of existing T. vaginalis infections with antibiotics;and possibly vaccination. PHS 398/2590 (Rev. 11/07) Page Continuation Format Page